FIG 3.

Anti-CD137 MAb treatment reduces the number of germinal center B cells and FDCs. Four-week-old WT C57BL/6 male mice were inoculated with 10³ FFU of CHIKV-LR. At 2 dpi, 400 μg of agonistic anti-CD137 MAb or isotype-control MAb was administered via the i.p. route. (A to G) The numbers of total CD45⁺ leukocytes (A), CD3⁺ T cells (B), CD19⁺ B cells (C), PNA⁺ CD95⁺ or GL7⁺ CD95⁺ germinal center B cells (D and E), and CD45⁻ CD54⁺ CD21/CD35⁺ FDCs (F and G) in the spleen at 14 dpi were analyzed by flow cytometry. Representative flow cytometry dot plots of germinal center B cells (D) and FDCs (F) are shown. The numbers within the flow cytometry plots refer to the percentage of cells in the gated (boxed or circled) areas. (H) Serum was harvested at 30 dpi, and anti-CHIKV IgG titers were measured by ELISA. Each symbol represents an individual mouse, and bars indicate median values (with the exception of panel H, where mean values were used). Data were pooled from two or three experiments. *, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001; n.s., not significant, Mann-Whitney test.